Technological Field
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a multi-function apparatus thereof and a fixing device that fixes a toner image formed on a recording medium to the recording medium in such an image forming apparatus. Particularly, in a fixing device including an endless fixing belt that is wound to pass over a heating-side member and a nip forming member and a pressing roller that is driven to rotate in the state of being brought into tight contact with the nip forming member through the fixing belt and fixing a toner image to a recording medium in a nip portion at which the fixing belt and the pressing roller are brought into tight contact with each other by causing the pressing roller to be in tight contact with the fixing belt and driving the pressing roller to rotate, there is a feature in that the fixing belt is stably rotated in the state of being in tight contact with the nip forming member by decreasing frictional resistance between the fixing belt and the nip forming member by employing a simple configuration.
Description of the Related Art
Generally, in an image forming apparatus such as a copying machine, a printer, a facsimile, or a multi-function apparatus thereof, a toner image transferred onto a recording medium is fixed onto the recording medium by using a fixing device.
In such a fixing device, in fixing a toner image transferred to a recording medium to a sheet by using heat and pressure, in order to save energy, an endless fixing belt is wound to pass over a heating roller and a heating-side roller, the pressing roller is driven to rotate in the state of being in tight contact with the heating-side roller through the fixing belt, and the toner image is fixed to a recording medium at a nip portion at which the fixing belt and the pressing roller are tightly brought into contact with each other.
In addition, in recent years, in order to further save energy, for example, as disclosed in JP 2008-46663 A, it is proposed that, instead of the heating-side roller described above, by using a fixing member, in which a heat-resistant elastic member is disposed at a portion at which a nip is formed by causing the pressing roller to be in tight contact therein, that does not rotate, the fixing belt described above is wound to pass over a heating roller and the fixing member, and, by causing the pressing roller that is driven to rotate to be in tight contact with the heat-resistant elastic member through the fixing belt, the fixing belt is driven to rotate together with the pressing roller, and, in a nip portion at which the fixing belt and the pressing roller are brought into tight contact with each other, a toner image is fixed to a recording medium.
However, in the technology disclosed in JP 2008-46663 A, sliding resistance is generated according to friction between the heat-resistant elastic member of the fixing member and the fixing belt, and the rotation of the fixing belt becomes unstable, whereby there is a problem of the presence of an adverse effect on a formed image and the like.
In addition, as disclosed in JP 2003-337481 A, a fixing device fixing an unfixed image on a recording material is known. When devices configuring an image forming apparatus are compared with each other, the power consumption of the fixing device is relatively high. In order to decrease the power consumption of the image forming apparatus, it is effective to decrease the power consumption of the fixing device.
The fixing device fixes an unfixed image through pressurization and heating. As one of techniques for decreasing the power consumption of the fixing device, it is considered to lower the fixing temperature. In a case where the fixing temperature is set to be low, in order to suppress the degradation of the image quality (fixing quality), it is necessary to employ some countermeasure.
For example, in a case where same toner is used, by increasing the load at the fixing nip or increasing a nip time, the influence according to the lowering of the fixing temperature can be decreased. Also in a case where the fixing temperature is lowered, by employing such a countermeasure, degradation of the fixing quality can be suppressed, and furthermore, the power consumption of the fixing device can be decreased.